1. Field of the Invention
The present invention relates to an ink for ink-jet recording.
2. Description of the Related Art
A copper complex coloring agent, such as a copper phthalocyanine dye, a copper phthalocyanine pigment and the like, is used as a cyan coloring agent for an ink for ink-jet recording.
Generally, an anticorrosive, such as benzotriazole and the like, is used in inks for ink-jet recording, in order to prevent corrosion of a metal material in contact with the ink in an ink passage of an ink-jet head.
When benzotriazole is added to an ink for ink-jet recording comprising a copper complex coloring agent, the benzotriazole is coordinated to free copper ions released from the copper complex coloring agent, and a precipitate is formed in the ink. This causes a problem that nozzles of an ink-jet head are clogged. This problem is particularly significant when the concentration of the free copper ions released from the copper complex coloring agent in the ink for ink-jet recording is 0.01 ppm or more.
In view of the above, an ink for ink-jet recording has been proposed in which the free copper ion concentration in the ink is reduced to 10 ppm or less by improving the degree of purification of a copper complex coloring agent or by using a sequestering agent.
However, it is difficult to purify the copper complex coloring agent to the extent that a precipitate caused by free copper ions is not formed. Moreover, the use of the sequestering agent in addition to the anticorrosive may adversely affect the components of an ink-jet head.